I found the wiki and thought I could add this there, but the link to make an account didn't work. This is just random stuff that may not be very interesting, but I just wanted to type it somewhere for completeness sake.

Instead of timing button presses for the Impossible Pogo Trick: If you hold jump, keen will jump once instead of jumping continuously; with Keen on the ground and the jump button still held, if the pogo button is pressed, Keen will jump with Impossible Pogo Trick height. This can also be done while running. Doing the Impossible Pogo Trick this way makes it easier (for me) to quickly double-tap the pogo button in order to get the height of the pogo trick while immediately putting the pogo stick away for the increased control Keen has without the pogo stick.

The ammo count has room for three digits. If you collect enough ammo to go over 999, you still get the ammo. The ammo count will only show the last three digits of the amount you have. I do not yet know the limit, partially because I lost count of the thousands digit.

I think the maximum ammo is 32767 (0x7FFF), since adding one more to that would overflow the 16-bit variable used to store the ammo count, causing it to wrap around to -32768.

Not really. I checked Keen 4 EGA v1.4 (Apogee release) and the In-game logic doesn't care about the actual value of the ammo variable. As long as the ammo is not zero, you can still fire new shots, which means the maximum ammo value would be 65535 (0xFFFF). Only the status menu and the optional ammo objects treat the variable as a signed 16-bit variable, everything else doesn't seem to care.

So the maximum amount of ammo you can have without causing some minor bugs is 32767. The actual limit (with some bugs) is 65535. Adding one more to that would overflow any 16-bit variable and the value would become 0 again.

Wow. I have been busy for quite a while and haven't added this to the wiki.

One problem is that I am not sure how to phrase it. I wonder if there is some terminology I can use so I don't phrase it as awkwardly as I did in my first post. Anyone who comes up with a decent way of explaining it is welcome to post it.